Dylan Thompson

Muscular soreness following prolonged intermittent high-intensity shuttle running

The aim of this study was to examine the impact of prolonged intermittent high-intensity shuttle running on soreness and markers of muscle damage. Sixteen males took part in the study, half of whom were assigned to a running group and half to a resting control group. The exercise protocol involved 90 min of intermittent shuttle running and walking (Loughborough Intermittent Shuttle Test: LIST), reflecting the activity pattern found in multiple-sprint sports such as soccer. Immediately after exercise, there was a significant increase (P < 0.05) in serum activities of creatine kinase and aspartate aminotransferase, and values remained above baseline for 48 h (P < 0.05). Median peak activities of creatine kinase and aspartate aminotransferase occurred 24 h post-exercise and were 774 and 43 U x l(-1), respectively. The intensity of general muscle soreness, and in the specific muscles investigated, was greater than baseline for 72 h after the shuttle test (P < 0.05), peaking 24-48 h post-exercise (P < 0.05). Muscle soreness was not correlated with either creatine kinase or aspartate aminotransferase activity. Soreness was most frequently reported in the hamstrings. Neither soreness nor serum enzyme activity changed in the controls over the 4 day observation period. It appears that unaccustomed performance of prolonged intermittent shuttle running produces a significant increase in both soreness and markers of muscle damage.

Peak power output, the lactate threshold, and time trial performance in cyclists

PURPOSE To determine the relationship between maximum workload (W(peak)), the workload at the onset of blood lactate accumulation (W(OBLA)), the lactate threshold (W(LTlog)) and the D(max) lactate threshold, and the average power output obtained during a 90-min (W(90-min)) and a 20-min (W(20-min)) time trial (TT) in a group of well-trained cyclists. METHODS Nine male cyclists (.VO(2max) 62.7 +/- 0.8 mL.kg(-1).min(-1)) who were competing regularly in triathlon or cycle TT were recruited for the study. Each cyclist performed four tests on an SRM isokinetic cycle ergometer over a 2-wk period. The tests comprised 1) a continuous incremental ramp test for determination of maximal oxygen uptake (.VO(2max) (L.min(-1) and mL.kg(-1).min(-1)); 2) a continuous incremental lactate test to measure W(peak), W(OBLA), W(LTlog), and the D(max) lactate threshold; and 3) a 20-min TT and 4) a 90-min TT, both to determine the average power output (in watts). RESULTS The average power output during the 90-min TT (W(90-min)) was significantly (P < 0.01) correlated with W(peak) (r = 0.91), W(LTlog) (r = 0.91), and the D(max) lactate threshold (r = 0.77, P < 0.05). In contrast, W(20-min) was significantly (P < 0.05) related to .VO(2max) (L.min(-1)) (r = 0.69) and W(LTlog) (r = 0.67). The D(max) lactate threshold was not significantly correlated to W(20-min) (r = 0.45). Furthermore, W(OBLA) was not correlated to W(90-min) (r = 0.54) or W(20-min) (r = 0.23). In addition, .VO(2max) (mL.kg(-1).min(-1)) was not significantly related to W(90-min) (r = 0.11) or W(20-min) (r = 0.47). CONCLUSION The results of this study demonstrate that in subelite cyclists the relationship between maximum power output and the power output at the lactate threshold, obtained during an incremental exercise test, may change depending on the length of the TT that is completed.

Time course of changes in inflammatory markers during a 6-mo exercise intervention in sedentary middle-aged men: a randomized-controlled trial.

Regular exercise may improve systemic markers of chronic inflammation, but direct evidence and dose-response information is lacking. The objective of this study was to examine the effect and time course of changes in markers of chronic inflammation in response to progressive exercise training (and subsequent detraining). Forty-one sedentary men 45-64 yr of age completed either a progressive 24-wk exercise intervention or control followed by short-term removal of the intervention (2-wk detraining). Serum IL-6 fell by -0.4 pg/ml (SD 0.6) after 12 wk and responded to moderate-intensity exercise. Serum alanine aminotransferase (ALT) activity fell -7 U/l (SD 11) at 24 wk although there was no evidence of any change by week 12 (and therefore ALT required more vigorous-intensity activity and/or a more prolonged intervention). The effect on IL-6 was lost after 2-wk detraining whereas the change in ALT was retained. The temporal fall and rise in IL-6 with training and subsequent detraining in men with high IL-6 at baseline provided a retrospective opportunity to examine parallel genomic changes in peripheral mononuclear cells. A subset of 53 probes was differentially regulated by at least twofold after training with 31 of these changes being lost after detraining (n = 6). IL-6 responded quickly to the carefully monitored exercise intervention (within weeks) and required only moderate-intensity exercise, whereas ALT took longer to change and/or required more vigorous-intensity exercise. Further work is required to determine whether any of the genes that temporally changed in parallel with changes in IL-6 are a cause or consequence of this response.

The causal role of breakfast in energy balance and health: a randomized controlled trial in obese adults

Background: The causal nature of associations between breakfast and health remain unclear in obese individuals. Objective: We sought to conduct a randomized controlled trial to examine causal links between breakfast habits and components of energy balance in free-living obese humans. Design: The Bath Breakfast Project is a randomized controlled trial with repeated measures at baseline and follow-up among a cohort in South West England aged 21–60 y with dual-energy X-ray absorptiometry–derived fat mass indexes of ≥13 kg/m2 for women (n = 15) and ≥9 kg/m2 for men (n = 8). Components of energy balance (resting metabolic rate, physical activity thermogenesis, diet-induced thermogenesis, and energy intake) were measured under free-living conditions with random allocation to daily breakfast (≥700 kcal before 1100) or extended fasting (0 kcal until 1200) for 6 wk, with baseline and follow-up measures of health markers (e.g., hematology/adipose biopsies). Results: Breakfast resulted in greater physical activity thermogenesis during the morning than when fasting during that period (difference: 188 kcal/d; 95% CI: 40, 335) but without any consistent effect on 24-h physical activity thermogenesis (difference: 272 kcal/d; 95% CI: −254, 798). Energy intake was not significantly greater with breakfast than fasting (difference: 338 kcal/d; 95% CI: −313, 988). Body mass increased across both groups over time but with no treatment effects on body composition or any change in resting metabolic rate (stable within 8 kcal/d). Metabolic/cardiovascular health also did not respond to treatments, except for a reduced insulinemic response to an oral-glucose-tolerance test over time with daily breakfast relative to an increase with daily fasting (P = 0.05). Conclusions: In obese adults, daily breakfast leads to greater physical activity during the morning, whereas morning fasting results in partial dietary compensation (i.e., greater energy intake) later in the day. There were no differences between groups in weight change and most health outcomes, but insulin sensitivity increased with breakfast relative to fasting. This trial was registered at www.isrctn.org as ISRCTN31521726.

Nonprescribed physical activity energy expenditure is maintained with structured exercise and implicates a compensatory increase in energy intake

BACKGROUND Exercise interventions elicit only modest weight loss, which might reflect a compensatory reduction in nonprescribed physical activity energy expenditure (PAEE). OBJECTIVE The objective was to investigate whether there is a reduction in nonprescribed PAEE as a result of participation in a 6-mo structured exercise intervention in middle-aged men. DESIGN Sedentary male participants [age: 54 ± 5 y; body mass index (in kg/m²): 28 ± 3] were randomly assigned to a 6-mo progressive exercise (EX) or control (CON) group. Energy expenditure during structured exercise (prescribed PAEE) and nonprescribed PAEE were determined with the use of synchronized accelerometry and heart rate before the intervention, during the intervention (2, 9, and 18 wk), and within a 2-wk period of detraining after the intervention. RESULTS Structured prescribed exercise increased total PAEE and had no detrimental effect on nonprescribed PAEE. Indeed, there was a trend for greater nonprescribed PAEE in the EX group (P = 0.09). Weight loss in the EX group (-1.8 ± 2.2 kg compared with +0.2 ± 2.2 kg in the CON group, P < 0.02) reflected only ≈40% of the 300-373 kcal/kg body mass potential energy deficit from prescribed exercise. Serum leptin concentration decreased by 24% in the EX group (compared with 3% in the CON group, P < 0.03), and we estimate that this was accompanied by a compensatory increase in energy intake of ≈100 kcal/d. CONCLUSIONS The adoption of regular structured exercise in previously sedentary, middle-aged, and overweight men does not result in a negative compensatory reduction in nonprescribed physical activity. The less-than-predicted weight loss is likely to reflect a compensatory increase in energy intake in response to a perceived state of relative energy insufficiency.

Acute moderate-intensity exercise in middle-aged men has neither an anti- nor proinflammatory effect

Strenuous exercise induces an initial pro- and subsequent anti-inflammatory response, and it has been suggested that this may be one of the ways that regular exercise reduces chronic inflammation and therefore the risk of cardiovascular disease. However, public health recommendations emphasize moderate-intensity physical activity, and it is important to understand whether moderate-intensity exercise has a similar anti-inflammatory effect. Twelve sedentary male volunteers (age 54 +/- 4 yr) completed two main trials, moderate-intensity exercise and rest (30 min at 50% maximal oxygen uptake vs. sitting, respectively). There were no significant changes in circulating neutrophils, lymphocytes, monocytes, or serum interleukin-6, interleukin-10, and C-reactive protein concentration over the 7 days following exercise. Similarly, lymphocyte adhesion to cultured endothelial cells and heme oxygenase-1 (HO-1) expression in lymphocytes and monocytes were not affected by walking at any time point. These results suggest that the long-term anti-inflammatory and antiatherogenic effects of regular moderate-intensity physical activity must be explained by something other than a profound net anti-inflammatory response to each exercise bout since a single bout of walking did not lead to a change in various markers of inflammation or lymphocyte adherence to cultured endothelial cells.

The impact of adiposity on adipose tissue-resident lymphocyte activation in humans

Background/objectives:The presence of T lymphocytes in human adipose tissue has only recently been demonstrated and relatively little is known of their potential relevance in the development of obesity-related diseases. We aimed to further characterise these cells and in particular to investigate how they interact with modestly increased levels of adiposity typical of common overweight and obesity.Subjects/methods:Subcutaneous adipose tissue and fasting blood samples were obtained from healthy males aged 35–55 years with waist circumferences in lean (<94 cm), overweight (94–102 cm) and obese (>102 cm) categories. Adipose tissue-resident CD4+ and CD8+ T lymphocytes together with macrophages were identified by gene expression and flow cytometry. T lymphocytes were further characterised by their expression of activation markers CD25 and CD69. Adipose tissue inflammation was investigated using gene expression analysis and tissue culture.Results:Participants reflected a range of adiposity from lean to class I obesity. Expression of CD4 (T-helper cells) and CD68 (macrophage), as well as FOXP3 RNA transcripts, was elevated in subcutaneous adipose tissue with increased levels of adiposity (P<0.001, P<0.001 and P=0.018, respectively). Flow cytometry revealed significant correlations between waist circumference and levels of CD25 and CD69 expression per cell on activated adipose tissue-resident CD4+ and CD8+ T lymphocytes (P-values ranging from 0.053 to <0.001). No such relationships were found with blood T lymphocytes. This increased T lymphocyte activation was related to increased expression and secretion of various pro- and anti-inflammatory cytokines from subcutaneous whole adipose tissue explants.Conclusions:This is the first study to demonstrate that even modest levels of overweight/obesity elicit modifications in adipose tissue immune function. Our results underscore the importance of T lymphocytes during adipose tissue expansion, and the presence of potential compensatory mechanisms that may work to counteract adipose tissue inflammation, possibly through an increased number of T-regulatory cells.

Confusion and Conflict in Assessing the Physical Activity Status of Middle-Aged Men

BACKGROUND Physical activity (including exercise) is prescribed for health and there are various recommendations that can be used to gauge physical activity status. The objective of the current study was to determine whether twelve commonly-used physical activity recommendations similarly classified middle-aged men as sufficiently active for general health. METHODS AND FINDINGS We examined the commonality in the classification of physical activity status between twelve variations of physical activity recommendations for general health in ninety men aged 45-64 years. Physical activity was assessed using synchronised accelerometry and heart rate. Using different guidelines but the same raw data, the proportion of men defined as active ranged from to 11% to 98% for individual recommendations (median 73%, IQR 30% to 87%). There was very poor absolute agreement between the recommendations, with an intraclass correlation coefficient (A,1) of 0.24 (95% CI, 0.15 to 0.34). Only 8% of men met all 12 recommendations and would therefore be unanimously classified as active and only one man failed to meet every recommendation and would therefore be unanimously classified as not sufficiently active. The wide variability in physical activity classification was explained by ostensibly subtle differences between the 12 recommendations for thresholds related to activity volume (time or energy), distribution (e.g., number of days of the week), moderate intensity cut-point (e.g., 3 vs. 4 metabolic equivalents or METs), and duration (including bout length). CONCLUSIONS Physical activity status varies enormously depending on the physical activity recommendation that is applied and even ostensibly small differences have a major impact. Approximately nine out of every ten men in the present study could be variably described as either active or not sufficiently active. Either the effective dose or prescription that underlies each physical activity recommendation is different or each recommendation is seeking the same prescriptive outcome but with variable success.

Exercise counteracts the effects of short-term overfeeding and reduced physical activity independent of energy imbalance in healthy young men.

•  Physical exercise significantly improves health but to what extent these benefits depend on altered energy balance remains unclear. •  In a human experimental model, we investigated whether daily exercise could counteract the effects of short‐term overfeeding and under‐activity independent of its impact on energy imbalance in healthy young men. •  Short‐term positive energy balance from overfeeding and under‐activity resulted in impaired metabolic outcomes and alterations in the expression of several key genes within adipose tissue involved in nutritional balance, metabolism and insulin action. •  These changes were mostly prevented by the addition of a daily vigorous‐intensity exercise bout even in the face of a standardised energy surplus.

Effects of carbohydrate and caffeine ingestion on performance during a rugby union simulation protocol.

Abstract In this study, we investigated the effect of ingesting carbohydrate alone or with caffeine on performance of a rugby union-specific shuttle running protocol. On three occasions, at least one week apart in a counterbalanced trial order, eight male rugby union forwards ingested either placebo or carbohydrate (1.2 g · kg−1 body mass · h−1) before and during a rugby union-specific protocol, with pre-exercise caffeine ingestion (4 mg · kg−1) before one of the carbohydrate trials (carbohydrate + caffeine). The intermittent exercise protocol included walking, jogging, and cruising at pre-determined intensities, simulated contact events, a sustained high-intensity test of speed and agility (Performance Test), and a 15-m sprint. Ratings of perceived exertion (RPE) were recorded every 5 min and a motor skills test was performed after each 21-min block. Performance Test times were not significantly different between trials but the likelihood of 2% improvements for carbohydrate + caffeine over placebo and carbohydrate were 98% and 44%, respectively. For carbohydrate + caffeine, 15-m sprints were faster than for placebo (P=0.05) and the motor skills test was performed faster in the carbohydrate + caffeine trial than the carbohydrate and placebo trials (P < 0.05), while RPE was lower in the carbohydrate + caffeine trial than the carbohydrate and placebo trials (P < 0.05). The results indicate a likely benefit to rugby performance following co-ingestion of carbohydrate and caffeine.